Exam 10: Transaction Management and Concurrency Control

To ensure consistency of the database,every transaction must begin with the database in an unstable state.

A consistent database is ____.

A ____ lock prevents the use of any tables in the database from one transaction while another transaction is being processed.

A ____ lock locks the entire diskpage.

Incomplete or improper transactions can have a devastating effect on database integrity.

Durability requires that all portions of the transaction must be treated as a single,logical unit of work in which all operations are applied and completed to produce a consistent database.

The DBMS guarantees that the semantic meaning of a transaction truly represents the real-world event.

Most real-world database transactions are formed by only one database request.

A shared lock produces no conflict as long as all the concurrent transactions are read-write only.

The scheduler establishes the order in which the operations within concurrent transactions are executed.

Explain the functions of shared and exclusive locks.

During the ____ phase,a transaction scans the database,executes the needed computations,and makes the updates to a private copy of the database values.

Database transaction ____________________ restores a database from an inconsistent state to a previously consistent state.

A ____ lock allows concurrent transactions to access different rows of the same table.

If T1 has not unlocked data item Y,T2 cannot begin; if T2 has not unlocked data item X,T1 cannot continue.Consequently,T1 and T2 each wait for the other to unlock the required data item.Such a deadlock is also known as a(n)____________________.

A single-user database system automatically ensures ____ of the database,because only one transaction is executed at a time.

The objective of ____________________ control is to ensure the serializability of transactions in a multiuser database environment.

The transaction recovery write-ahead-log protocol ensures that transaction logs are always written before any database data are actually updated.

When you read from or update a database,you create a transaction.

The ____________________ interleaves the execution of database operations to ensure serializability.